1. Field of the Invention
The present invention relates generally to lens modules, and particularly to a lens module with multi-step focuses.
2. Description of Related Art
With the development of the optical imaging technology, camera devices are becoming widely used in electronic devices, such as digital cameras and mobile phones.
A camera device generally has a focus structure, to capture images of an object with different magnifications. The focus structures of camera devices can be divided into two kinds of focus structure: an optical focus structure and an auto focus structure. The optical focus structure achieves different magnifications by a driving device thereof or by users driving a lens of a lens module of the camera device to a desired position. Generally, a space is required to move the lens and an image sensor in the camera device with the optical structure. In contrast, the auto focus structure focuses on an object by comparing the images of the object with the images on the image sensor. The image sensor is controlled by a processing unit installed inside the camera device. When it comes to obtain an image of the object, the processing unit magnifies the image in the image sensor. The auto focus structure is suitable for compact styles of camera devices. However, a problem accompanying auto focus camera devices is that the definition of the image is reduced when the image is magnified.
In order to cater for the compact style trend of the camera devices, and insure that clear magnified images can be obtained, a magnetic driving device is employed to drive a lens in a lens module of the camera device. Referring to US Patent Publication No. 2004/0130808 A1, a magnetic driving device in a lens module is illustrated. The magnetic driving device comprises an annular driving magnet attached to a periphery of a lens mounted on a movable member, and an immovable member equipped with a driving coil. When electrical current is given to the driving coil, the driving coil is activated and drives the movable member with the lens to move along the optical axis of the lens from a first position to a second position. However, images with different magnifications are highly demanded by users, the related camera device can not achieve multi-magnifications, therefore the camera device needs to be improved.
What is needed therefore is a lens module with multi-step focuses can provide multi-magnifications in use.